Problem: Jessica starts counting at 34, and she counts by threes. If 34 is the 1st number that Jessica counts. what is the 15th number that she counts?
Answer: What is the first number that she counts? $34$ What is the second number that she counts? $\begin{align*}&34 + 3 \\ &= 37\end{align*}$ What is the third number that she counts? $\begin{align*}&34 + 3 + 3 \\ &= 34 + (2 \times 3) \\ &= 40\end{align*}$ What is the 15th number that she counts? $\begin{align*}&34 + (14\times3) \\ &= 34 + 42 \\ &= 76\end{align*}$